Arthritic diseases are chronic, crippling conditions for which there are no cures. We, and others, have shown that direct intra-articular injection of certain recombinant viral vectors can provide expression of therapeutic transgenes at levels sufficient to halt arthritis in animal models. Further, we have recently demonstrated that with the use of immunologically compatible vectors and cDNAs, exogenous transgenes can be expressed indefinitely in the joints of experimental animals. A primary barrier to clinical translation of gene therapies for chronic joint disease has been the lack of suitable vector systems. In this regard, recombinant adeno- associated virus (AAV) offers many advantages: it is nonpathogenic, of low immunogenicity, and enables persistent transgene expression in many applications. The capacity to cross-package, or pseudotype, the AAV2 vector has significantly expanded the versatility of this system, providing the opportunity to enhance transgenic expression as well as the potential to evade pre-existing immunity. Currently 9 AAV capsid serotypes are being developed as vectors for gene therapy applications. The recent development of double- stranded, self-complementary (sc) AAV vectors overcomes previous limitations associated with inefficient second strand DNA synthesis in articular tissues such that AAV vectors can be realistically considered for human application. Beyond the capacity of AAV vectors to deliver exogenous genes to joint tissue and achieve short-term functional expression, very little is known specifically of the biology of this system in the context of the articular environment. Thus, the goal of this project is to develop an understanding of the pharmacokinetics of AAV vector serotypes 1-9 intra-articularly to facilitate the clinical application of this technology in a safe, rational and effective manner. In Specific Aim 1, using a nude rat model to avoid issues of immune interference, we will establish local and systemic transgene delivery and expression profiles for AAV serotypes 1-9 following intra-articular administration. In Aim 2 we will perform similar experiments in an arthritic model to determine how morphologic changes associated with inflammatory disease affect AAV-mediated gene delivery and expression. For Aim 3, using immunologically competent animals we will determine the capacity to enhance or rescue AAV-mediated transgene expression by repeat vector administration and the use of alternate vector serotypes. In Aim 4 we will determine the impact of prior natural infection with wild type AAV2 on transgene delivery and expression of recombinant AAV vectors of the same and alternate serotypes.